Water-soluble mineral tanning agent



Patented Sept. 10, 1929.

GEORG KRENZLEIN, ARTHUR VOSS, AND

FRANZ BRUNNTRAGER, OF HOCHST-OlxT-THE- MIAIN, GERMANY, ASSIGIIOBLS'TOGENER'AL ANIL'XNLE VJGRKS, INC., OF NE'W YORK,

N. Y., A oonrona rrou or ELAW RE;

' WATER-SOLUBLE MINERAL TANNING AGENT.

No Drawing. Application filed April is, lees, seriar ia onsae, and. Germany a rn 24 1925.

Our present invention relates to mineral tanning agents, which possess excellent solubility in water, and to processes for preparing the same.

We have found that the tanning properties of the basic chromium salts can be considerably improved by I combining them with water-soluble salts of the alkaline earth metals for instance calcium or metals closely re lated thereto, such as salts of zinc or of magncsium, the combination being effected in such a manner that no reaction-products which are insoluble in water are formed. Thus for example, it is possible, by combining one molecule of basic chromium sulphate,

with two molecules of magnesium sulpl'iate, O to obtain a chromium preparation which dissolves sul'liciently Well in Water. If a product is prepared in the same molecular proportion as indicated above, in which the chromium sulphate possesses, for example, a basicity of 33 ,4; to 50%, then the basic chromium magnesium sulphate so obtained is easily soluble in cold water, in contrast to a chromium sulphate ot the same basicity prepared Without any additional components. lhe basicity of basic chromium compounds depends upon the 39 number of hydroxyi groups in a molecule of the compound. Thus (Infill-D is usually referred to as having a basicity of 100% and Cr, (OH) ,Cl, is 50% basic and 01.,(Ol'l) 61 is 331.4 basic.

Besides the advantage of great solubility, the compounds of this invention possess other advantages. Although the ability to separate from the solutions in'flakes is diminished, a tl'iorough tanning is obtained considerably faster with the combination tanning salts than with the simple chromium salts of the same basicity. Consequently the yield of the chrome tanning liquors is greater, and the leathers obtained by the use of equal amounts of chromium are more plump and compact in the case of the products of the above process.

The leathers obtainable by the new comm hined process are distinguished by a remarle ably light color and their stability while i being stored. V 1

The process otpreparing the combination tanning salts, above referred to, may be varied according to the metallic components of the tanning-agent used. For instance for preparing the mixed chromiumsalts the process may be carried out as abovestated by mix ing a basic chromium salt with the second component, or; by mixing the, neutral chromium salt with the salt of the bivalent metal, and ell'ecting the necessary basici'ty by adding a base to the aqueous solution of the two salts. r i

The inventionis ing examples:

(1) 412 parts by weight of 100 chromium hydroxide are mixed with 740 parts by weight of crystallized magnesiumsulphate and 2,000 parts of water and 1,110 par 1.23 specific gravity sulphuric acid are allowed to run in while stirring at C. A clear solution is obtained from which: the greater part oil water is separated by evapora-o tion in a vacuum. The solid product ob tained, which is allowed to separate in its best form as abright green powder, by means of suitable apparatus, although it is not by: groscopic, is very easily soluble in cold. water, It can be used directly forchrome tanning. For. the tanning of,100 parts of hides, enough of the product prepared inExample 1 is dissolved in three times its weight of water, so that, according to the'character of the leather desired, 1.7 to 2.25 parts of 'chro-; miumooxide are made use of. This tanning solution is added in three portions during the course of an hour to the fparts of hides, which are fulled ina tanning vat. with parts of water and two, parts of sodium chloride. ,Atter fulling, for three to four hours, a plump, soft leathcrot fine grain and fast to boiling. is, obtained,

illustrated the "followts by weight of r 2 400 ojartsbyiweight of 100% chi-Q5 l nnum hydroxide are mixed with the same amount of crystallized magnesium chloride, and 1,500 parts of water and 760 parts by weight of 1.17 sp. gr. hydrochloric acid are allowed to slowly run in et 90 Cjin the manner described inExample l. After the oxy-chloride which is difticultly soluble in water. Then this solution is dried on drums. The greenish powder obtained is easily soluble in water and yields excellent, almost ning by the usual methods.

' 'tained.

white leathers which are fast to boiling.

(4:) 412 parts by weight of 100% chromium hydroxide are mixed with 750 parts by weight of zinc sulphate in 2000 parts of water and 1110 parts by weight of 1.23 sp. gr. sulphuric acid are allowed to run in with stirring at 90 C. The clear solution ob tained is freed from the greater part of water by evaporation in a vacuum. The solid product obtained can be used for tan- Leathers of great fullness and soft to the touch are oh- (5) 400 parts by weight of chromium hydroxide and 380 parts by weight of aluminium sulphate are dissolved in 1500 parts of water and 950 parts by weight of 1.23 sp.- gr. sulphuric acid. By drying, a bright green powder of very good solubility and quick tanning action is obtained.

(6) 100.0 parts by weight of pickled hides are treated for an hour in a fullingvat comprising 59 parts by weight of chromium sulhate 52 artsb wei ht of ma nesium sul-' P a .P Y a a phate in 1500 parts of water and a soda solution containing 22.5 parts by-weight of calcined soda. After a further fulling of three hours, a soft, plump, fine grained leather is obtained.

In the appended claims, by the term alkaline earth metals are meant calcium, strontium, barium, magnesium and zinc.

We claim:

1. A new composition of matter compris ing a chromium salt having a basicity of at least. 33%,%,, and a water-soluble salt of an alkaline earth metal, said composition of matter being an excellent chromium tanning agent easily soluble in water. v

I 2. A new composition of matter comprising a chromium salt having a basicity 'of 33 3-5070 and a water-soluble (salt of an alkaline earth metal, said composition of matter being an excellent chromium tanning agent easily soluble in water.

3(A new. composition of matter comprising a chromium sulfate having a basicity of at least 33 and magnesium sulfate, said composition of matter being an excellent chromium tanning agent easily soluble in water.

GEORG KRANZLEIN. ARTHUR voss. FRANZ RRUNNTRAGRR. 

